1. Field of the Invention
This invention relates generally to tympanic thermometers and, more particularly, to an earplug having a thermochromic probe and stem that continuously monitors the core body temperature of the wearer and visually displays a first color in a temperature range considered to be normal for tympanic temperature and changes color reversibly upon detection of a temperature above or below that range to visually indicate to the wearer or an observer that the wearer has an unsafe core body temperature.
2. Background Art
Normal functioning of humans requires a body temperature of approximately 98.6° F. (37° C.). Hyperthermia is defined as elevated core body temperature of greater than 100.4° F. (38° C.). Hyperthermia occurs when the body produces or absorbs more heat than it can dissipate. It is usually caused by prolonged exposure to high temperatures. Mild hyperthermia is commonly called heat exhaustion or heat prostration, which is a serious medical emergency in which the body's core temperature rises to 100.4° F. (38° C.). Workers working in hot industrial and outdoor environments, such as for example roofers, firefighters, construction and factory workers, and athletes exercising strenuously in hot climates are susceptible to heat exhaustion. Common symptoms include headache, nausea, dizziness, fatigue, irritability, and confusion. Severe hyperthermia is called heat stroke. Heat stroke may come on suddenly, but it usually follows the untreated milder stages. Heat stroke is the most serious heat related medical emergency in which the body's temperature regulating system fails and the core body temperature can rise to dangerous levels greater than 104° F. (40° C.). Symptoms of heat stroke include hot, dry skin, lack of sweating, a very fast pulse, confusion and perhaps seizures or coma. If untreated, heat stroke can lead to death or permanent disability.
Hypothermia is the opposite of hyperthermia which is present in heat exhaustion and heat stroke. Hypothermia is defined as any body temperature below 95.0° F. (35.0° C.). It is subdivided into four different degrees: mild 0.90-95° F. (32-35° C.); moderate, 82-90° F. (28-32° C.); severe, 68-82° F. (20-28° C.); and profound at less than 68° F. (20° C.). As body temperature decreases, characteristic symptoms occur such as shivering and mental confusion. In severe hypothermia, all body functions are decreased, including heart rate, breathing rate, metabolism blood pressure and mental activity. Difficulty in speaking, sluggish thinking, and amnesia start to appear; inability to use hands and stumbling is also usually present. Cellular metabolic processes shut down. Below 86° F. (30° C.), the exposed skin becomes blue and puffy, muscle coordination becomes very poor, walking becomes almost impossible, and the person exhibits incoherent/irrational behavior. If core body temperature is lower than 82° F. (28° C.), the condition is life-threatening without immediate medical attention.
The hypothalamus is located in the base of the brain and acts as the body's thermostat. It functions by monitoring heat sensors throughout the body and adjusting the temperature based on the body's needs. The goal of the hypothalamus is to maintain the body's core temperature (the temperature of the heart, lungs, liver, kidneys, brain, etc.) between 96.9° F. to 100.4° F. (36° to 38° C.). It is well recognized that the tympanic membrane within the ear canal is an excellent site for determination of the core temperature of a body due to its proximity to the external carotid artery which supplies blood to the hypothalamus. Patients show changes in core temperature at the tympanic membrane prior to peripheral sites such as the mouth or rectum.
It is well known that the tympanic region of the ear canal follows the core body temperature with high fidelity. This region includes the tympanic membrane and the adjacent walls of the ear canal. Most conventional ear thermometers, also known as aural thermometers and tympanic thermometers have a short tube or probe that is placed into the ear canal and measure the heat that is emitted from the tympanic membrane of the eardrum by means of an infrared detector on the device and a digital readout is given. Most all ear thermometers position the end of the probe or a sensor adjacent to, but not in contact with, the tympanic membrane. Generally, therefore, not the tympanic membrane temperature is taken, which is considered as being representative of the true core body temperature, but rather an intermediate value that lies between the temperature of the tympanic membrane and the ear canal temperature.
The commonly accepted average core body temperature (measured internally) is 98.6° F. (37° C.). The typical oral (under the tongue) measurement is slightly cooler, at 97.5° F. to 98.9° F. (36.4° C. to 37.2° C.), and temperatures of 95.9° F. to 99.5° F. (35.5° C. to 37.5° C.) is considered normal for tympanic temperature.
Casali et al, U.S. Pat. No. 5,333,622 discloses a custom-molded earplug for swimming protection, hearing protection, and the like, fabricated in situ by depositing a foaming material within a person's ear and allowing the foaming material to form foam. Acoustic and electronic equipment such as a Helmholtz resonator or other tuned device capable of modifying sound waves, a communications transmitter, a communications receiver, a communications transceiver, a hearing aid, an ear microphone, a personal earphone, and a hearing test transducer or probe tube can be fabricated in the ear in a similar fashion. Temperature sensing elements may also be incorporated within or positioned by the foaming material to provide an in the ear thermometer.
Fraden et al, U.S. Pat. No. 6,773,405 discloses a continuous core body temperature monitor in the form of a pliable ear plug that conforms to the shape of an ear canal and incorporates a temperature sensor that is clamped between the plug and the ear canal wall. The external surface of the plug is connected to an external temperature sensor and a heating element that compensate for a heat lost from the ear canal to the environment by maintaining the temperature gradient between the temperature sensor and the heating element close to zero.
Falco et al, U.S. Pat. No. 6,622,816 discloses earplugs wherein an energy-activated color change material is included within or on the earplug that exhibits a visual change upon exposure to thermal energy to indicate a proper fit. When inserted into a wearer's ears, the earplug interacts with the thermal energy in the interior of the ear canal and changes color creating at least two visual zones. A first zone is the color of the earplug prior to insertion and a second visual zone is the color of the earplug when it is exposed to and is absorbing thermal energy from the interior of the ear canal. The edge of the change in color will spread to at least a portion of the exterior portion of the earplug, or the entire earplug, enough to be visually apparent to an observer that a proper fit has been achieved for maximum attenuation. The '816 patent only determines a proper fit and teaches that the color change occurs when the temperature where the earplug is located is at about 50° F. to about 90° F. (about 10° C. to 32.2° C.), which is well below the normal average core body temperature considered normal for tympanic temperature of humans.